[Elecraft] Re: Help, I think I've killed my K1

Sat Feb 22 05:33:10 2003

Thanks for your input Bob and Mike.  Once again I marvel
at the level of expertise this list provides!  Here's what I
found.

I picked up a NTE988 regulator this afternoon from
a local supplier.  It was a bit of a battle to get the blown
chip un-soldered and out, but fortunately the NTE988 is an
exact fit and same pin out.  I quickly went through the
applicable DC resistance checks on the FP board just to
make sure, and all was OK.  With some trepidation, I put
everything back together and fired up the rig.  I used the
internal 8 cell NiMH battery pack (about 10.2 volts at the
time) just to keep voltages down a bit for initial checkout.

Well, the LED's come on, the relays clicked and the LCD
read the band and frequency.  So far so good.  An antenna
soon proved the RX was working, with sweet CW on 40m.
I have not tried to transmit.  For I quickly began to find
anomalies occurring:  1. A distinct hum on each press of the
front panel press-switches; 2. An internal volt-meter that now
displayed the battery pack voltage as 14.4volts!; 3. And
eventually I found that pressing the "switch filters" button
caused the MCU to go into hang up mode.  I can switch
off and on again and it comes to back to life.

So it seems that Bob was EXACTLY right.  The 6.2 volts
of the NTE988 causes some spooky stuff to happen with
the MCU.  So it seems that I will just have to wait to get
a proper ZR78L06C from Elecraft or elsewhere.  At least
I think I have shown that it WAS indeed the 6v regulator that
blew, and hopefully nothing else.

Again thanks for all the help.

73 John, N6JW

----- Original Message -----
From: Bob - AG5Q <[email protected]>
To: Morrow, Michael A. <[email protected]>; John Webster
<[email protected]>; <[email protected]>
Sent: Friday, February 21, 2003 5:30 PM
Subject: Re: [Elecraft] Re: Help, I think I've killed my K1

> The 7.5V spec means the device can survive that much voltage without
damage
> but it's only guaranteed to work like a microprocessor up to 6.0V.
>
> The 78L06 can be as much as 6.15V and there are a lot of  K1s and K2s that
> get by with that, so I wouldn't be surprised it yours works at 6.2V.  For
> non-critical applications, that's okay, but sometimes the problems that
are
> caused by the voltage being out-of tolerance can be very tough to
determine.
> "Is it the micro itself or is it some random input causing the problem?"
>
> I just mentioned the possibility, so if you do see irregular operation,
you
> can switch back to the 78L06.
>
> 73/ Bob - AG5Q
>
>
> ----- Original Message -----
> From: "Morrow, Michael A." <[email protected]>
> To: "'Bob - AG5Q'" <[email protected]>; "John Webster" <[email protected]>;
> <[email protected]>
> Sent: Friday, February 21, 2003 7:13 PM
> Subject: RE: [Elecraft] Re: Help, I think I've killed my K1
>
>
> >
> > Bob / AG5Q wrote:
> >
> > > The NTE-988 is speced at 6.2V rather than 6.0V like the ZR78L06.
> > >
> > > This will mean running the 16C77 at 6.2V which is slightly
> > > higher than it's spec limit of 6.0.
> >
> > I think it would be OK.  The max. voltage rating spec for 16C7x devices
on
> > Vdd above Vss (logic ground) is 7.5 volts.
> >
> > 73,
> > Mike / KK5F
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